netfilter: nft_ct: keep counters away from CONFIG_NF_CONNTRACK_LABELS

This is accidental, they don't depend on the label infrastructure.

Fixes: 48f66c90 ("netfilter: nft_ct: add byte/packet counter support")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Florian Westphal <fw@strlen.de>